Strip materials that can be severed into lengths to form at least parts of fasteners are well known, typical examples being those described in U.S. Pat. Nos. 3,009,235; 3,138,841; 3,577,607; 3,708,837; 3,770,359; 4,024,003; and 4,290,832.
Several of these patents describe strip materials including a backing which can be woven or comprise a nonfibrous polymeric layer and a multiplicity of lengths of longitudinally oriented flexible resilient polymeric monofilament, each of which lengths includes a central bight portion secured in the backing by weaving, fusing or both, two stem portions extending from the opposite ends of the bight portion which project generally normal to a major surface of the backing, and enlarged heads at the ends of the stem portions opposite the backing formed by heating those ends.
It is well known in the fastener art that the heads of such strip material will releasably engage with loops projecting from a backing (called loop material herein). The heads of such strip material will be strongly held by the loops of such loop material when an attempt is made to separate the strip and loop materials by moving their backings in a direction parallel to each other because the loops can then engage around the stem portions under the heads. The loops will hold the heads with much less strength when an attempt is made to move the backings of the strip and loop materials away from each other in a direction generally normal to the major surface of the strip material, however, since the heads have surfaces adjacent the backing which are generally planar and extend at generally a right angle radially from their supporting stem portions so that the loops cannot firmly engage those head surfaces. Thus to provide fastener portions that the loops can firmly engage under such conditions (such as may be desirable to fasten a seat cover fabric lined with loop material to a molded seat cushion), manufacturers have resorted to molding lengths of strip material that include a backing, a plurality of stems projecting normally from a major surface of the backing, and heads on the ends of the stems opposite the backing, each of which heads has two hook-like portions spaced from its supporting stem and projecting along the stem toward the backing (e.g., "Molded Velcro Arrowhead #8 Tape" available from Velcro Industries Limited, New York, N.Y.). Such hooks can be firmly engaged by the loops when the backings are moved away from each other in a direction generally normal to the major surface of the strip material, but molded strip material is not without its disadvantages. For example, the strength and flexibility of a molded stem is less than the strength and flexibility of a similar sized stem made from a longitudinally oriented monofilament; only two hooks can easily be molded on each head and those hooks on each head must be oriented in the same direction relative to the backing which might limit the ability of the loops of some loop materials to engage the hooks; it is difficult to make molded strip material with closely spaced stems, or to vary the spacing between stems to change the holding ability of the molded strip material; and the backing layer is rather stiff for some applications where flexibility is desirable.